This study of membrane transport is targeted to provide the basic scientific information needed to determine the mechanisms by which physiological control systems and homeostatic mechanisms are altered in the aged. Membrane vesicles derived from the luminal brush border segment and the antiluminal basal-lateral region of the renal tubule and intestinal epithelial cell plasma membrane are used. Topics investigated include: 1) the mechanism of the Na ion gradient-dependent uptake of D-glucose; 2) the mechanisms and specificities of amino acid transport systems; 3) the mechanism and regulation of phosphate transport; 4) the mechanism of D-glucose-dependent Na ion transport; 5) the mechanism of sulfate transport; 6) inositol transport, the mechanism of inosituria in hyperglycemia; 7) the uptake of aminoglycosides (gentamicin) and its relationship to nephrotoxicity; 8) molecular organization and orientation of membrane components in the membrane components in the membrane; 9) the isolation and characterization of the Na ion gradient-dependent glucose carrier by reconstitution of synthetic membranes; and 10 changes in membrane function with age.